Chemical elements
    Physical properties
    Chemical properties
      Boron Hydrides
      Boron trihydride
      Boron halogen
      Boron trifluoride
      Hydrofluoboric acid
      Potassium borofluoride
      Fluoboric acid
      Perfluoboric acid
      Boron subchloride
      Boron trichloride
      Boron tribromide
      Boron tri-iodide
      Oxides of Boron
      Tetraboron trioxide
      Boron dioxide
      Tetraboron pentoxide
      Boron sesqui-oxide
      Boron trioxide
      Boric anhydride
      Boric Acids
      Orthoboric acid
      Boric acid
      Boracic acid
      Complex Boric Acids
      Perboric Acid and Perborates
      Sodium perborate
      Sodium hyperborate
      Potassium perborate
      Rubidium perborate
      Ammonium perborate
      Barium perborate
      Boron sesquisulphide
      Boron trisulphide
      Boron pentasulphide
      Boron selenide
      Boron nitride
      Boron amide
      Boron imide
      Boron phosphide
      Boron phospho-iodides
      Boron carbide
      Boron thiocyanate
      Boron Alkyls
      Boron trimethyl
      Boron Silicides and

Boron dioxide, B2O2

This oxide may be prepared as follows. Crude magnesium boride, made as described below, is decomposed by cold water; the filtered solution is then treated by either of the following processes: (i.) the solution is evaporated to dryness in vacuo and the residue heated; (ii.) the solution is treated with ammonia, filtered from magnesium hydroxide, and evaporated to dryness in vacuo and the residue heated. In method (i.) part of the boron dioxide obtained is present in combination with magnesia (as a magnesium borite); in method (ii.) the dioxide is obtained practically free from magnesia but contaminated with about five per cent, of the lower oxide B4O3.2H2O.

Boron dioxide is soluble in water. Its aqueous solution can be oxidised to boric acid by evaporation in air or by heating with nitric acid, but is not affected by iodine. Freezing-point measurements indicate that the molecular formula of the oxide is B2O2. The oxide apparently combines with water to form an acid, and the aqueous solution dissolves an amount of freshly precipitated magnesium hydroxide corresponding to the production of a magnesium borite, MgO.2B2O2.

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